Traditionally, for connecting relatively soft synthetic resin tube, for example, a soft vinyl chloride tube of an AVF needle, with a hard tubular connector for medical use such as of polycarbonate or a needle base (hub), there is a method of bonding with a solvent or adhesive, or a method called blocking in which the aforementioned connector or needle base (hub) is inserted into the aforementioned soft vinyl chloride tube and the whole assembly is subjected to a heating environment to connect the two together. An example of the problem which arises when adopting the aforementioned method of bonding with a solvent and adhesive include degradation, embrittlement, and solvent cracking of the material due to the solvent. Also, in the blocking method, there is a problem that heating the entire assembly will cause the heat shrinkage of the entire body thereby leading to unstable product dimensions after blocking, and further there is a risk that keeping the assembly in a heating environment for long hours will cause the stabilizer etc. contained in the resin constituting respective parts to bleed out thus leading to degradation and color change of the material.
Further, as a method of connecting thermoplastic members, there is proposed in the patent documents 1, 2, and 3 a method of connecting thermoplastic tube members, in which an electrically terminated annular conductor is interposed between the inner surface of a large-diameter thermoplastic tube member and the outer surface of a small-diameter thermoplastic tube member, the tip of a small-diameter tube member being inserted into and connected to the large-diameter tube member, and the aforementioned conductor is caused to generate Joule heat uniformly in its circumferential direction through high frequency induction heating from outside the large-diameter tube member thereby melting and fusing the constituent material of the tube members in the region where the conductor is interposed.    Patent document 1: JP, A, 09-290461    Patent document 2: JP, A, 53-128166    Patent document 3: JP, A, 53-128167